Bifurcation stent and method of positioning in a body lumen

ABSTRACT

A method of deploying a bifurcation stent at a vascular bifurcation of a main vessel into first and second branch vessels includes: positioning a bifurcation stent at a vascular bifurcation, the bifurcation stent expandable from a reduced diameter to an expanded diameter, the bifurcation stent comprising a first end, a second end, and a marker near the first end, wherein the first end diameter is larger than the second end diameter when the bifurcation stent is expanded, and wherein the bifurcation stent is positioned such that the marker is approximately aligned with a carinal plane at the vascular bifurcation; partially expanding the first end of the bifurcation stent; adjusting the position of the bifurcation stent such that the marker is positioned past the carinal plane and towards the first branch vessel; and deploying the bifurcation stent at the bifurcation. Devices are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.11/737,652, filed Apr. 19, 2007, now U.S. Pat. No. 7,686,846, which is acontinuation-in-part of U.S. application Ser. No. 10/225,484, filed Aug.20, 2002, now U.S. Pat. No. 7,238,197, which is a continuation-in-partof U.S. application Ser. No. 09/580,597, filed May 30, 2000, now U.S.Pat. No. 6,666,883, which is a continuation-in-part of U.S. applicationSer. No. 09/011,214, filed Apr. 3, 1998, now U.S. Pat. No. 6,068,655,which is the national stage of International Application No.PCT/FR97/00999, filed Jun. 5, 1997, which claims priority from FrenchApplication No. 2749500, filed Jun. 6, 1996, the disclosures of whichare all incorporated by reference in their entireties.

BACKGROUND

1. Field

The present invention relates to an apparatus permitting the treatmentof bodily conduits, typically blood vessels, in an area of abifurcation, e.g., in an area where a principal conduit separates intotwo secondary conduits. It also relates to equipment and methods forpositioning the apparatus.

2. Description of the Related Art

It is known to treat narrowing of a rectilinear blood vessel by means ofa radially expandable tubular device, commonly referred to as a stent.This stent is introduced in the unexpanded state into the internal lumenof the vessel, in particular by the percutaneous route, as far as thearea of narrowing. Once in place, the stent is expanded in such a way asto support the vessel wall and thus re-establish the appropriate crosssection of the vessel.

Stent devices can be made of a non-elastic material, in which case thestent is expanded by an inflatable balloon on which it is engaged.Alternatively, the stent can be self-expanding, e.g., made of an elasticmaterial. A self-expanding stent typically expands spontaneously whenwithdrawn from a sheath which holds it in a contracted state.

For example, U.S. Pat. Nos. 4,733,065 and 4,806,062, which areincorporated by reference herein, illustrate existing stent devices andcorresponding positioning techniques.

A conventional stent is not entirely suitable for the treatment of anarrowing situated in the area of a bifurcation, since its engagementboth in the principal conduit and in one of the secondary conduits cancause immediate or delayed occlusion of the other secondary conduit.

It is known to reinforce a vascular bifurcation by means of a stentcomprising first and second elements, each formed by helical winding ofa metal filament. The first of the two elements has a first part havinga diameter corresponding to the diameter of the principal vessel, and asecond part having a diameter corresponding to the diameter of a firstone of the secondary vessels. The first element is intended to beengaged in the principal vessel and the second element is intended to beengaged in the first secondary vessel. The second element has a diametercorresponding to the diameter of the second secondary vessel. After thefirst element has been put into place, the second element is thencoupled to the first element by engaging one or more of its turns in theturns of the first element.

This equipment permits reinforcement of the bifurcation but appearsunsuitable for treating a vascular narrowing or an occlusive lesion, inview of its structure and of the low possibility of radial expansion ofits two constituent elements.

Moreover, the shape of the first element does not correspond to theshape of a bifurcation, which has a widened transitional zone betweenthe end of the principal vessel and the ends of the secondary vessels.Thus, this equipment does not make it possible to fully support thiswall or to treat a dissection in the area of this wall. Additionally,the separate positioning of these two elements is quite difficult.

SUMMARY

A method of deploying a bifurcation stent at a vascular bifurcation of amain vessel into first and second branch vessels includes positioning abifurcation stent at a vascular bifurcation, the bifurcation stentexpandable from a reduced diameter to an expanded diameter, thebifurcation stent comprising a first end, a second end, and a markernear the first end, wherein the first end diameter is larger than thesecond end diameter when the bifurcation stent is expanded, and whereinthe bifurcation stent is positioned such that the marker is aligned witha carinal plane at the vascular bifurcation; partially expanding thefirst end of the bifurcation stent; adjusting the position of thebifurcation stent such that the marker is positioned past the carinalplane and towards the first branch vessel; and deploying the bifurcationstent at the bifurcation.

In one embodiment, the stent is self expandable. In another embodiment,the method further includes dilating the vascular bifurcation with adilation balloon prior to said positioning, expanding the first end ofthe bifurcation stent with a dilation balloon after said deploying,delivering a branch stent to the first branch vessel, and/or deliveringa second branch stent to the second branch vessel. In some embodiments,the branch stent is deployed such that it partially overlaps a portionof the bifurcation stent.

In one embodiment, the vascular bifurcation is selected from the groupconsisting of one or more of a coronary artery, a carotid artery, afemoral artery, an iliac artery, a popliteal artery, and a renal artery.In another embodiment, partially expanding the first end includespartially retracting a sheath that surrounds the bifurcation stent. Thesheath can include one or more retaining bands.

In another embodiment, a method of deploying a stent at a bifurcation ofa main vessel to two branch vessels, the two branch vessels forming acarina at the bifurcation, includes: partially deploying a stent at thebifurcation; advancing the stent towards the branch vessels so the stentat least partially straddles the carina; and deploying the stent at thebifurcation. The method can further include expanding a balloon at thebifurcation.

In another embodiment, a bifurcation stent includes: a plurality ofcells extending along a longitudinal axis of the bifurcation stent froma first end to a second end of the bifurcation stent, each cell having aplurality of struts extending in a substantially linear, zig-zag patternextending around the bifurcation stent, wherein the bifurcation stent isexpandable from reduced diameter to an expanded diameter, the first endof the bifurcation stent having a larger diameter than the second endwhen expanded; and an eyelet integrally formed with the cell positionedadjacent the first end, and configured to receive a radiopaque markertherein.

In some embodiments, the bifurcation stent also includes a radiopaquemarker, which can be mushroom-shaped. In some embodiments, theradiopaque marker is press-fit into the eyelet. The radiopaque markercan include gold or tantalum. In some embodiments, the radiopaque markeris selected to have an electromotive force to match the stent. In oneembodiment, the bifurcation stent also includes a second eyeletintegrally formed with the cell positioned adjacent the second end andconfigured to receive a second radiopaque marker therein.

BRIEF DESCRIPTION OF THE DRAWINGS

Having thus summarized the general nature of the invention, certainpreferred embodiments and modifications thereof will become apparent tothose skilled in the art from the detailed description herein havingreference to the attached figures, of which:

FIG. 1 is a side view of a first embodiment of a stent system shown inan expanded state;

FIG. 2 is a perspective, partial cutaway view of the stent system ofFIG. 1 shown in a state of radial contraction, as disposed on a deliverycatheter;

FIG. 3 is a longitudinal sectional view of a bifurcation treatable bythe stent system of FIG. 1;

FIG. 4 is a section view of the bifurcation of FIG. 3 showing a deliverycatheter positioned therein;

FIG. 5 is a section view of the bifurcation of FIG. 3 showing anembodiment of a stent system shown in a partially contracted state on aportion of a delivery catheter;

FIG. 6 is a section view of the bifurcation of FIG. 3 showing anembodiment of a stent system shown in an expanded and fully deployedstate;

FIG. 7 is a section view of a bifurcation presenting an aneurysm and anembodiment of a stent system shown deployed therein,

FIG. 8 is a side view of a stent system according to a second embodimentshown in an expanded state;

FIG. 9 is a plan view of a delivery catheter usable to deploy a stentsystem having certain features and advantages;

FIG. 9A is an alternative embodiment of a proximal handpiece of thedelivery catheter of FIG. 9;

FIG. 9B is an alternative embodiment of the delivery catheter of FIG. 9;

FIG. 9C is a section view of a portion of the delivery catheter of FIG.9 taken through line 9C-9C and specifically showing an alternative pullwire lumen;

FIG. 9D is a section view of a portion of the delivery catheter of FIG.9 taken through line 9D-9D and specifically showing a retaining band;

FIG. 9E is a detail view of a retraction band retention assembly of thedelivery catheter of FIG. 9;

FIG. 10 is a partial cutaway view of a distal portion of the catheter ofFIG. 9 including a stent system disposed thereon;

FIG. 10A is an alternative embodiment of a distal end assembly of thedelivery catheter of FIG. 9B;

FIG. 10B is a detail view of a distal portion of the outer sheath shownin FIG. 10;

FIG. 10C is a section view taken along the line 10C-10C of FIG. 10;

FIG. 11A is a plan view of a transitional portion of the catheter ofFIG. 9;

FIG. 11B is a cross sectional view of the transitional portion takenalong the line 11B-11B of FIG. 11A;

FIG. 11C is a transverse sectional view of the transitional portiontaken along the line 11C-11C of FIG. 11A;

FIG. 11D is a cross sectional view of the proximal shaft taken along theline 11D-11D of FIG. 11A;

FIG. 12 is a side section view of a distal portion of an embodiment of adelivery catheter having certain features and advantages;

FIG. 13 is a section view of a bifurcation showing an embodiment of adelivery catheter positioned therein;

FIG. 14 is a section view of a bifurcation showing a first stent in apartially deployed state;

FIG. 15 is a section view of a bifurcation showing a first stent in afully deployed state;

FIG. 16 is a section view of a bifurcation showing a second stent in apartially deployed state;

FIG. 17 is a section view of a bifurcation showing a second stent in afully deployed state;

FIG. 18 is a section view of a bifurcation as in FIG. 17, with a secondbranch stent deployed in the second branch;

FIG. 19 is a schematic elevation view of a single-stent delivery systemfor delivering a cylindrical stent;

FIG. 20 is a schematic elevation view of the single-stent deliverysystem of FIG. 19 showing the sheath in a proximal detail view;

FIG. 21 is a schematic elevation view of a single-stent delivery systemfor delivering a conical stent;

FIG. 22 is a schematic elevation view of the single-stent deliverysystem of FIG. 21 showing the sheath in a proximal detail view;

FIG. 23A is a side view of a tapered bifurcation stent in accordancewith one embodiment of the present invention;

FIG. 23B is the sidewall pattern of the bifurcation stent of FIG. 23Ashown in a compressed orientation;

FIG. 23C is a side view of an alternate tapered stent of the presentinvention.

FIG. 23D is an enlarged view of a marker retention band;

FIG. 23E is a side elevational view of a marker prior to mounting in amarker retention band;

FIG. 23F is a perspective view of a mounted marker in a stent of thepresent invention.

FIG. 24A is a side view of a tapered bifurcation stent in accordancewith another embodiment of the present invention;

FIG. 24B is the sidewall pattern of the bifurcation stent of FIG. 24A;and

FIGS. 25-31 illustrate the delivery of a bifurcation stent to a vascularbifurcation.

DETAILED DESCRIPTION

As described above, the attached Figures illustrate a stent system andcorresponding delivery system for use in treating vessels (e.g.,conduits) within the human body at areas of bifurcations. FIG. 3 shows abifurcation 30 in which a main conduit or vessel 32 separates into twosecondary branch conduits or vessels 34. The stent system generallyincludes a pair of dissimilar stents specifically designed for use in anarea of a bifurcation 30. Such dissimilar stents are then disposed on anelongate catheter for insertion into the human body. The dissimilarstents may be self-expanding or manually expandable such as by a balloonabout which the stents may be disposed as will be described in furtherdetail below.

FIG. 1 shows one embodiment of an expandable stent system 10 permittingthe treatment of bodily conduits in the area of a bifurcation such asthat shown. The stent system 10, shown in an expanded state in FIG. 1,generally comprises first 12 and second 14 stent portions which may eachbe divided into two segments, thus creating four successive segments 22,24, 26, 28, of meshwork structure. The first stent 12 is generallyadapted to be disposed in a branch conduit or vessel 34 of abifurcation, while the second stent 14 is generally adapted to bedisposed in a main vessel 32 (see FIG. 3). If desired, the segments maybe connected to one another via one or more bridges of material 18. Thestents 12, 14 are generally movable between a contracted position and anexpanded position. As will be clear to those skilled in the art, thestents may be self-expanding or balloon-expandable.

According to the illustrated embodiment, the stents 12, 14 generallycomprise an expandable mesh structure which includes a plurality of meshcells 36. The mesh cells 36 of these segments are in one embodimentelongated in the longitudinal direction of the stents 12, 14 and have ineach case a substantially hexagonal shape in the embodiment shown. Thoseskilled in the art will recognize that the mesh used to form the stentsegments 22, 24, 26, and 28 may comprise a variety of other shapes knownto be suitable for use in stents. For example a suitable stent maycomprise mesh with repeating quadrilateral shapes, octagonal shapes, aseries of curvatures, or any variety of shapes such that the stent isexpandable to substantially hold a vessel or conduit at an enlargedinner diameter.

The first stent 12 may be divided into two segments 22 and 24 which maybe identical to each other and typically have a tubular shape with adiameter which is substantially greater than the diameter of one of thesecondary branch conduits 34. Those skilled in the art will recognizethat the first stent may comprise a variety of shapes such that itfunctions as described herein. The first stent 12 may be expandable to asubstantially cylindrical shape having a constant diameter along itslength. The first stent 12 may comprise a range of lengths depending onthe specific desired location of placement. For example, the length ofthe first stent 12 will typically be between about 1 and about 4centimeters as desired.

The second stent 14 is preferably adapted to be deployed in closeproximity to the first stent 12, and may also be divided into upper 26and lower 28 segments. The lower segment 28 of the second stent 14typically has a tubular cross-sectional shape and has an expandeddiameter which is substantially greater than the diameter of theprincipal conduit 32 (FIG. 3). The upper segment 26 of the second stent14 preferably comprises a larger diameter at its distal (upper) end 38than at its proximal (lower) end 40. In one embodiment the upper segmentof the second stent portion comprises a substantially conical shape. Inan alternative embodiment, the second stent 14 may be tapered radiallyoutward along its entire length in the distal direction. In eitherembodiment however, the expanded diameter of the distal end 38 of thesecond stent 14 is preferably substantially larger than the expandeddiameter of the proximal end 42 of the first stent 12. For example, thedistal end 38 of the second stent 14 may expand to a diameter that is atleast about 105%, and preferably at least about 110%, and in someembodiments as much as 120% or more, of the diameter of the proximal end42 of the first stent 12. The second stent 14 may comprise a range oflengths depending on the specific desired location of placement. Forexample, the second stent 14 will typically be between 1 and 4centimeters as desired.

In its expanded state, as shown in FIG. 1, the upper segment 26 of thesecond stent 14 typically has mesh cells 36 whose width increasesprogressively, compared to that of the meshes of the lower segment 28,on the one hand in the longitudinal sense of the dual stent device 10,in the direction of the distal end 38 of the second stent 14, and, onthe other hand, in the transverse sense of the second stent 14, in thedirection of a generatrix diametrically opposite that located in thecontinuation of the bridge 18. Alternatively stated, the upper segment26 of the second stent 14 preferably comprises a mesh with multiplecellular shapes 36 which may have larger dimensions at a distal end 38of the stent 14 than those at the proximal end 40 such that the secondstent 14 expands to a substantially funnel shape.

In the embodiment shown, this increase in the width of the mesh cells 36results from an increase in the length of the edges 48 of the mesh cells36 disposed longitudinally, as well as an increase in the angle formedbetween two facing edges 48.

This segment 26 thus may have a truncated shape with an axis which isoblique in relation to the longitudinal axis of the first stent 12 whenexpanded. This shape, for example, corresponds to the shape of thebifurcation shown in the area of the widened transitional zone 46 (FIG.3) which separates the end of the principal conduit 32 (see FIG. 3) fromthe ends of the secondary conduits 34. In a preferred embodiment, thesecond stent 14 is placed in close proximity to the first stent 12. Forexample, the distal end 38 of the second stent 14 is preferably placedwithin a distance of about 4 mm of the distal end 42 of the first stent12, more preferably this distance is less than about 2 mm, and mostpreferably the stents are placed within 1 mm of one another.

In the embodiment shown in FIG. 1, the distance between first and secondstents 12, 14 is held substantially fixed by the provision of a bridge18 between them. Bridges 18 may be provided to join the first and secondstents 12, 14 to one another and/or to join the upper and lower segments22, 24 and 26, 28 of each stent 12 and 14 together. If present, thebridges 18 may connect the adjacent ends of the segments 22, 24 and 26,28 and typically have a small width, so that they can undergo a certainflexion, making it possible to orient these segments in relation to oneanother, in particular the lower segment 24 of the first stent 12 inrelation to the upper segment 26 of the second stent 14.

In addition, in other embodiments, the bridges 18 could be integral withone of the connected segments and separately connected, such as bywelding, to the other connected segment. For example, the bridge 18which connects the first and second stents 12, 14 could be integral withthe upper segment 26 of the second stent 14 and connected to lowersegment 24 of the first segment 26. Alternatively, the bridge 18 couldbe integral with the lower segment 24 of the first stent 12 andconnected to the upper segment 26 of the second stent 14.

In yet other embodiments, bridges 18 could be separate pieces ofmaterials which are separately connected to segments 22, 24, 26, 28 suchas by welding, adhesion, or other bonding method. In all of theseembodiments, the first stent 12 can be made from different pieces ofmaterial than the second stent 14. A tube from which the first stent 12may be made (e.g., by laser cutting techniques) may comprise a smallerdiameter than a tube from which the second stent 14 may be made. Therespective tubes may or may not be made of the same material.Alternatively, the first and second stent may be formed from a singlepiece of material.

When the segments 26 and 28 of the second stent 14 are made from tubesof a smaller diameter than the segments 22 and 24 of the first stent 12,the radial force of the first stent segments 22 and 24 is larger thanthe radial force of the second stent segments 26 and 28, especially atlarger cross sections.

Accordingly, bridges 18 can be made from one of these tubes, and thus beintegral with segments 22 and 24 or segments 26 and 28. Alternatively,the bridges 18 can be separate pieces of material.

In further embodiments, bridges 18 are omitted such that the individualsegments are spaced as desired during installation and use. Theseindividual segments are still delivered and implanted in the same coreand sheath assembly.

The bridges 18 between two consecutive segments could be greater orsmaller in number than six, and they could have a shape other than anomega shape, permitting their multidirectional elasticity, and inparticular a V shape or W shape.

For example, FIG. 8 shows an alternative embodiment of the stent system10 with first 12 and second 14 stents shown in their unconstrained,expanded states. According to this embodiment, each stent 12, 14 may bedivided into two segments 22, 24 and 26, 28 and may include one or moreflexible bridges 18 connecting the first 12 and second stents 14 to oneanother. In this embodiment, the two consecutive segments 22, 24 and 26,28 of the first and second stents 12 and 14, are connected by aplurality (e.g., six) omega-shaped bridges 50. The curved central part52 of these bridges 50 may have a multidirectional elasticity permittingthe appropriate longitudinal orientation of the various segments inrelation to one another. The advantage of these bridges 50 is that theyprovide the stent with longitudinal continuity, which facilitates thepassage of the stent system into a highly curved zone and whicheliminates the need to reduce this curvature, (which may be dangerous inthe cases of arteriosclerosis).

Thus, the stent system 10 of FIG. 8 can comprise several segments 22,24, 26, 28 placed one after the other, in order to ensure supplementarysupport and, if need be, to increase the hold of the stents in thebifurcation 30. The upper segment 26 of the second stent 14 could havean axis coincident with the longitudinal axis of the first stent, andnot oblique in relation to this axis, if such is rendered necessary bythe anatomy of the bifurcation which is to be treated.

Alternatively, the lower segment 24 of the first stent 12 could itselfhave, in the expanded state, a widened shape similar to that of thesecond stent and corresponding to the shape of the widened connectingzone (increasing diameter in the proximal direction) by which, incertain bifurcations, the secondary conduits 34 (see FIG. 3) areconnected to the widened transition zone 46. Thus, the lower segment 24of the first stent 12, or the entire first stent 12 may have a firstdiameter at its distal end, and a second, larger diameter at itsproximal end with a linear or progressive curve (flared) taper inbetween. According to this embodiment, this segment 24 would thus have ashape corresponding to the shape of this widened connecting zone, andwould ensure perfect support thereof.

One method of making a self-expanding stent is by appropriate cutting ofa sheet of nickel/titanium alloy (for example, an alloy known by thename NITINOL may appropriately be used) into a basic shape, then rollingthe resulting blank into a tubular form. The blank may be held in acylindrical or frustroconical form by welding the opposing edges of thisblank which come into proximity with each other. The stent(s) may alsobe formed by laser cutting from metal tube stock as is known in the art.Alternatively, a stent may be formed by selectively bending and forminga suitable cylindrical or noncylindrical tubular shape from a single ormultiple wires, or thin strip of a suitable elastic material. Thoseskilled in the art will understand that many methods and materials areavailable for forming stents, only some of which are described herein.

Some Nickel Titanium alloys are malleable at a temperature of the orderof 10° C. but can recover a neutral shape at a temperature substantiallycorresponding to that of the human body. FIG. 2 shows the stent system10 (see FIG. 1) disposed on a delivery catheter in a state of radialcontraction. In one embodiment, a self-expanding stent may be contractedby cooling its constituent material of nickel-titanium or othershape-memory alloy to a temperature below its transformationtemperature. The stent may later be expanded by exposing it to atemperature above the transformation temperature. In the present use, ashape-memory alloy with a transformation temperature at or below normalbody temperature may be used. Those skilled in the art will recognizethat a self-expanding stent made of a substantially elastic material mayalso be mechanically contracted from its expanded shape by applying aradial compressive force. The stent may then be allowed to expand underthe influence of the material's own elasticity. Nickel titanium andother alloys such as such as Silver-Cadmium (Ag—Cd), Gold-Cadmium(Au—Cd) and Iron-Platinum (Fe₃—Pt), to name but a few offer desirablesuperelastic qualities within a specific temperature range.

In one embodiment, the contraction of a stent may cause the mesh celledges 48 to pivot in relation to the transverse edges 49 of the meshcells 36 (see FIG. 3) in such a way that the mesh cells 36 have, in thisstate of contraction, a substantially rectangular shape. Those skilledin the art will recognize that other materials and methods ofmanufacturing may be employed to create a suitable self-expanding stent.

Alternatively, the stents used may be manually expandable by use of aninflatable dilatation balloon with or without perfusion as will bediscussed further below. Many methods of making balloon-expandablestents are known to those skilled in the art. Balloon expandable stentsmay be made of a variety of bio-compatible materials having desirablemechanical properties such as stainless steel and titanium alloys.Balloon-expandable stents preferably have sufficient radial stiffness intheir expanded state that they will hold the vessel wall at the desireddiameter. In the case of a balloon-expandable second stent 14, theballoon on which the second stent 14 is disposed may be specificallyadapted to conform to the desired shape of the second stent 14.Specifically, such a balloon will preferably have a larger diameter at adistal end than at a proximal end.

The present discussion thus provides a pair of dissimilar stentspermitting the treatment of a pathological condition in the area of abifurcation 30. This system has the many advantages indicated above, inparticular those of ensuring a perfect support of the vessel wall and ofbeing relatively simple to position.

For the sake of simplification, the segment which has, in theunconstrained expanded state, a cross section substantially greater thanthe cross section of one of the secondary conduits will be referred tohereinafter as the “secondary segment”, while the segment which has, inthe expanded state, a truncated shape will be referred to hereinafter asthe “truncated segment.”

The secondary segment is intended to be introduced into the secondaryconduit in the contracted state and when expanded will preferably bearagainst the wall of the conduit. This expansion not only makes itpossible to treat a narrowing or a dissection situated in the area ofthe conduit, but also to ensure perfect immobilization of the apparatusin the conduit.

In this position, the truncated segment bears against the wall of theconduit delimiting the widened transitional zone of the bifurcation,which it is able to support fully. A narrowing or a dissection occurringat this site can thus be treated by means of this apparatus, withuniform support of the vascular wall, and thus without risk of this wallbeing damaged.

The two segments may be adapted to orient themselves suitably inrelation to each other upon their expansion.

Advantageously, at least the truncated segment may be covered by amembrane (for example, DACRON® or ePTFE) which gives it impermeabilityin a radial direction. This membrane makes it possible to trap betweenit and the wall of the conduit, the particles which may originate fromthe lesion being treated, such as arteriosclerotic particles or cellularagglomerates, thus avoiding the migration of these particles in thebody. Thus, the apparatus can additionally permit treatment of ananeurysm by guiding the liquid through the bifurcation and therebypreventing stressing of the wall forming the aneurysm.

The segments can be made from tubes of material of a different diameter,as discussed above, with the tube for the truncated segment having alarger diameter than the tube for the secondary segment. The tubes maybe made from the same material. The use of tubes of different diameterscan result in the truncated segment having a larger radial force,especially at larger diameters.

The apparatus can comprise several secondary segments, placed one afterthe other, to ensure supplementary support of the wall of the secondaryconduit and, if need be, to increase the anchoring force of the stent inthe bifurcation. To this same end, the apparatus can comprise, on thatside of the truncated segment directed toward the principal conduit, atleast one radially expandable segment having, in the expanded state, across section which is substantially greater than the cross section ofthe principal conduit.

These various supplementary segments may or may not be connected to eachother and to the two aforementioned segments by means of flexible links,such as those indicated above.

The flexible links can be integral with one of the segments andseparately connected to the other segment, or the flexible links can beseparate pieces of material separately connected to both segments, suchas by welding.

Preferably, the flexible link between two consecutive segments is madeup of one or more bridges of material connecting the two adjacent endsof these two segments. Said bridge or bridges are advantageously made ofthe same material as that forming the segments.

Each segment may have a meshwork structure, the meshes being elongatedin the longitudinal direction of the stent, and each one having asubstantially hexagonal shape; the meshes of the truncated segment mayhave a width which increases progressively in the longitudinal sense ofthe stent, in the direction of the end of this segment having thegreatest cross section in the expanded state.

This increase in the width of the meshes is the result of an increase inthe length of the edges of the meshes disposed longitudinally and/or anincrease in the angle formed between two facing edges of the same mesh.

In addition, the truncated segment can have an axis not coincident withthe longitudinal axis of the secondary segment, but oblique in relationto this axis, in order to be adapted optimally to the anatomy of thebifurcation which is to be treated. In this case, the widths of themeshes of the truncated segment also increase progressively, in thetransverse sense of the stent, in the direction of a generatrixdiametrically opposite that located in the continuation of the bridgeconnecting this segment to the adjacent segment.

The apparatus can be made of a metal with shape memory, which becomesmalleable, without elasticity, at a temperature markedly lower than thatof the human body, in order to permit retraction of the apparatus uponitself, and to allow it to recover its neutral shape at a temperaturesubstantially corresponding to that of the human body. This metal may bea nickel/titanium alloy known by the name NITINOL.

The deployment catheter for positioning the stent or stents comprisesmeans for positioning the stents and means for permitting the expansionof the stents when the latter are in place. These means can comprise acatheter having a removable sheath in which the stent is placed in thecontracted state, when this stent is made of an elastic material, or asupport core comprising an inflatable balloon on which the stent isplaced, when this stent is made of a nonelastic material.

In either case, this equipment comprises, according to the invention,means with which it is possible to identify and access, through the bodyof the patient, the longitudinal location of the truncated segment, sothat the latter can be correctly positioned in the area of the widenedzone of the bifurcation.

In the case where the expansion of this same segment is not uniform inrelation to the axis of the stent, the equipment additionally comprisesmeans with which it is possible to identify, through the body of thepatient, the angular orientation of the stent in relation to thebifurcation to be treated, so that the part of this segment having thegreatest expansion can be placed in a suitable manner in relation to thebifurcation.

Referring to FIG. 9, the stent system is generally deployed using anelongate flexible stent deployment catheter 100. Although primarilydescribed in the context of a multiple stent placement catheter withoutadditional functional capabilities, the stent deployment catheterdescribed herein can readily be modified to incorporate additionalfeatures such as an angioplasty balloon or balloons, with or withoutperfusion conduits, radiation or drug delivery capabilities, or stentsizing features, or be simplified to deploy only a single stent, or anycombination of these features.

The elongate delivery catheter 100 generally includes a proximal endassembly 102, a proximal shaft section 110 including a tubular body 111,a distal shaft section 120 including a distal tubular body 113, and adistal end assembly 107. The proximal end 102 may include a handpiece140 (see FIG. 9B), having one or more hemostatic valves and/or accessports 106, such as for the infusion of drugs, contrast media orinflation media in a balloon expandable stent embodiment, as will beunderstood by those of skill in the art. In addition, a proximalguidewire port 172 may be provided on the handpiece 140 in an over thewire embodiment (see FIG. 9A). The handpiece 140 (see FIG. 9B) disposedat the proximal end of the catheter 100 may also be adapted to controldeployment of the stents disposed on the catheter distal end 107 as willbe discussed.

The length of the catheter depends upon the desired application. Forexample, lengths in the area of about 120 cm to about 140 cm are typicalfor use in coronary applications reached from a femoral artery access.Intracranial or lower carotid artery applications may call for adifferent catheter shaft length depending upon the vascular access site,as will be apparent to those of skill in the art.

The catheter 100 preferably has as small an outside diameter as possibleto minimize the overall outside diameter (e.g., crossing profile) of thedelivery catheter, while at the same time providing sufficient columnstrength to permit distal transluminal advancement of the tapered tip122 (see FIG. 9). The catheter 100 also preferably has sufficient columnstrength to allow an outer, axially moveable sheath 114 (see FIG. 5) tobe proximally retracted relative to the central core 112 (see FIG. 7) inorder to expose the stents 118 (see FIG. 12). The delivery catheter 100may be provided in either “over-the-wire” or “rapid exchange” types aswill be discussed further below, and as will generally be understood bythose skilled in the art.

In a catheter intended for peripheral vascular applications, the outersheath 114 (see FIG. 5) will typically have an outside diameter withinthe range of from about 0.065 inches to about 0.092 inches. In coronaryvascular applications, the outer sheath 114 (see FIG. 5) may have anoutside diameter with the range of from about 0.039 inches to about0.065. Diameters outside of the preferred ranges may also be used,provided that the functional consequences of the diameter are acceptablefor the intended purpose of the catheter. For example, the lower limitof the diameter for any portion of catheter 100 in a given applicationwill be a function of the number of guidewire, pullwire or otherfunctional lumen contained in the catheter, together with the acceptableminimum flow rate of dilatation fluid, contrast media or drugs to bedelivered through the catheter and minimum contracted stent diameter.

The ability of the catheter 100 to transmit torque may also bedesirable, such as to avoid kinking upon rotation, to assist insteering, and in embodiments having an asymmetrical distal end on theproximal stent 14. The catheter 100 may be provided with any of avariety of torque and/or column strength enhancing structures, forexample, axially extending stiffening wires, spiral wrapped supportlayers, or braided or woven reinforcement filaments which may be builtinto or layered on the catheter 100. See, for example, U.S. Pat. No.5,891,114 to Chien, et al., the disclosure of which is incorporated inits entirety herein by reference.

Referring to FIG. 11D, there is illustrated a cross-sectional viewthrough the proximal section 106 of the catheter shaft 100 of FIG. 9B.The embodiment shown in FIG. 11D represents a rapid exchange embodiment,and may comprise a single or multiple lumen extrusion or a hypotubeincluding a pull wire lumen 220. In an over-the-wire embodiment, theproximal section 106 additionally comprises a proximal extension of aguidewire lumen 132 and a pull wire lumen 220. See FIG. 11C. Theproximal tube 111 may also comprise an inflation lumen in a ballooncatheter embodiment as will be understood by those skilled in the art.

At the distal end 107, the catheter is adapted to retain and deploy oneor more stents within a conduit of a human body. With reference to FIGS.10A and 12, the distal end assembly 107 of the delivery catheter 100generally comprises an inner core 112 (see FIG. 7), an axially moveableouter sheath 114 (see FIG. 5), and optionally one or more inflatableballoons 116 (FIG. 12). The inner core 112 (see FIG. 7) is preferably athin-walled tube at least partially designed to track over a guidewire,such as a standard 0.014 inch guidewire. The outer sheath 114 (see FIG.5) preferably extends along at least a distal portion 120 of the centralcore 112 (see FIG. 10) on which the stents 118 (see FIG. 12) arepreferably disposed.

The outer sheath 114 (see FIG. 5) may extend over a substantial lengthof the catheter 100, or may comprise a relatively short length, distalto the proximal guidewire access port 172 as will be discussed. Ingeneral, the outer sheath 114 (see FIG. 5) is between about 5 and about25 cm long.

Referring to FIG. 10, the illustrated outer sheath 114 comprises aproximal section 115, a distal section 117 and a transition 119. Theproximal section 115 has an inside diameter which is slightly greaterthan the outside diameter of the tubular body 113. This enables theproximal section 115 to be slideably carried by the tubular body 113.Although the outer sheath 114 may be constructed having a uniformoutside diameter throughout its length, the illustrated outer sheath 114steps up in diameter at a transition 119. The inside diameter of thedistal section 117 of outer sheath 114 is dimensioned to slideablycapture the one or more stents as described elsewhere herein. In astepped diameter embodiment such as that illustrated in FIG. 10, theaxial length of the distal section 117 from the transition 119 to thedistal end is preferably sufficient to cover the stent or stents carriedby the catheter 100. Thus, the distal section 117 in a two stentembodiment is generally at least about 3 cm and often within the rangeof from about 5 cm to about 10 cm in length. The axial length of theproximal section 115 can be varied considerably, depending upon thedesired performance characteristics. For example, proximal section 115may be as short as one or two centimeters, or up to as long as at leastabout 75% or 90% or more of the entire length of the catheter. In theillustrated embodiment, the proximal section 115 is generally within therange of from about 5 cm to about 15 cm long.

The outer sheath 114 and inner core 112 may be produced in accordancewith any of a variety of known techniques for manufacturing rapidexchange or over the wire catheter bodies, such as by extrusion ofappropriate biocompatible polymeric materials. Known materials for thisapplication include high and medium density polyethylenes,polytetrafluoroethylene, nylons, PEBAX, PEEK, and a variety of otherssuch as those disclosed in U.S. Pat. No. 5,499,973 to Saab, thedisclosure of which is incorporated in its entirety herein by reference.Alternatively, at least a proximal portion or all of the length ofcentral core 112 and/or outer sheath 114 may comprise a metal orpolymeric spring coil, solid walled hypodermic needle tubing, or braidedreinforced wall, as is understood in the catheter and guidewire arts.

The distal portion 117 of outer sheath 114 is positioned concentricallyover the stents 118 (see FIG. 12) in order to hold them in theircontracted state. As such, the distal portion 117 of the outer sheath114 is one form of a releasable restraint. The releasable restraintpreferably comprises sufficient radial strength that it can resistdeformation under the radial outward bias of a self-expanding stent. Thedistal portion 117 of the outer sheath 114 may comprise a variety ofstructures, including a spring coil, solid walled hypodermic needletubing, banded, or braided reinforced wall to add radial strength aswell as column strength to that portion of the outer sheath 114.Alternatively, the releasable restraint may comprise other elements suchas water soluble adhesives or other materials such that once the stentsare exposed to the fluid environment and/or the temperature of the bloodstream, the restraint material will dissolve, thus releasing theself-expandable stents. A wide variety of biomaterials which areabsorbable in an aqueous environment over different time intervals areknown including a variety of compounds in the polyglycolic acid family,as will be understood by those of skill in the art. In yet anotherembodiment, a releasable restraint may comprise a plurality oflongitudinal axial members disposed about the circumference of thestents. According to this embodiment anywhere from one to ten or moreaxial members may be used to provide a releasable restraint. The axialmembers may comprise cylindrical rods, flat or curved bars, or any othershape determined to be suitable.

In some situations, self expanding stents will tend to embed themselvesin the inner wall of the outer sheath 114 (see FIG. 5) over time. Asillustrated in FIGS. 9D and 10A, a plurality of expansion limiting bands121 may be provided to surround sections of the stents 12, 14 (see FIG.6) in order to prevent the stents from becoming embedded in the materialof the sheath 114 (see FIG. 5). The bands 121 may be provided in any ofa variety of numbers or positions depending upon the stent design. FIG.10A illustrates the bands positioned at midpoints of each of the fourproximal stent sections 127 and each of the five distal stent sections.In an alternative embodiment, the bands 121 are positioned over the endsof adjacent stent sections. The bands 121 may be made of stainlesssteel, or any other suitable metal or relatively non compliant polymer.Of course, many other structures may also be employed to prevent theself-expanding stents from embedding themselves in the plastic sheath.Such alternative structures may include a flexible coil, a braided tube,a solid-walled tube, or other restraint structures which will beapparent to those skilled in the art in view of the disclosure herein.

The inner surface of the outer sheath 114 (see FIG. 10), and/or theouter surface of the central core 112 (see FIG. 10) may be furtherprovided with a lubricious coating or lining such as Paralene, Teflon,silicone, polyimide-polytetrafluoroethylene composite materials orothers known in the art and suitable depending upon the material of theouter sheath 114 and/or central core 112 (see FIG. 10).

FIG. 10B shows a distal portion of sheath 114 received in an annularrecess 230 in the distal tip. As shown, at least the distal portion ofthe sheath 114 may comprise a two layer construction having an outertube 213 and an inner tube or coating 212. The exterior surface of theouter tube 213 is preferably adapted to slide easily within the vesselsto be treated, while the inner surface is generally adapted to have alow coefficient of static friction with respect to the stents, thusallowing the sheath to slide smoothly over the stents. The outer tube213 may, for example, be made of or coated with HDPE or PEBAX, and theinner tube 212 may, for example, be made of or coated with HDPE, PTFE,or FEP. In an embodiment in which the inner tube is made with a PTFEliner, however, the distal end 214 of the lubricious inner layer or tube212 is preferably spaced proximally from the distal end 216 of the outertube 213 by a distance within the range of from about 1 mm to about 3mm. This helps prevent the stent from prematurely jumping distally outof the sheath during deployment due to the high lubricity of the PTFEsurface.

FIG. 10 illustrates one embodiment of a sheath retraction system. Thesystem illustrated generally includes a sheath pull wire 222, a pullwire slot 224, a sheath retraction band 226, and an outer sheath 114.The sheath retraction band 226 may be a tubular element thermally oradhesively bonded or otherwise secured to a portion of the outer sheath114. In the illustrated embodiment, the retraction band 226 comprises asection of stainless steel tubing having an outside diameter of about0.055 inches, a wall thickness of about 0.0015 inches and an axiallength of 0.060 inches. However, other dimensions may be readilyutilized while still accomplishing the intended function. The sheathretraction band 226 is positioned within the distal portion 117 of theouter sheath 114, just distally of the diameter transition 119. Theretraction band 226 may be connected to the interior surface of theouter sheath 114 by heat fusing a pair of bands 225 (see FIG. 9E) to theinside surface of the outer sheath at each end of the retraction band.Alternatively, the retraction band 226 can be attached to the outersheath by using adhesives, epoxies, or by mechanical methods such ascrimping and swaging or a combination of these. In this manner, the pullforce which would be required to proximally dislodge the retraction band226 from the outer sheath 114 is greatly in excess of the proximaltraction which will be applied to the pull wire 222 in clinical use. Thedistal end of the pull wire 222 is preferably welded, soldered, bonded,or otherwise secured to the sheath retraction band 226. The pull wire222 may alternatively be bonded directly to the outer sheath.

Referring to FIG. 10, the pull wire slot 224 is preferably of sufficientlength to allow the sheath 114 to be fully retracted. Thus, the pullwire slot 224 is preferably at least as long as the distance from thedistal end of the stent stop 218 to the distal end of the sheath 114.Slot lengths within the range of from about 1 cm to about 10 cm arepresently contemplated for a two stent deployment system. With thesheath 114 in the distal position as shown, the pull wire slot 224 ispreferably entirely covered by the proximal portion 115 of the sheath114. Alternatively, in an embodiment in which the proximal extension ofsheath 114 extends the entire length of the catheter 100, discussedabove, sheath 114 can be directly attached to the control 150 (see FIG.9B), in which case a pull wire 222 and slot 224 as shown might not beused.

In yet another embodiment illustrated for example in FIGS. 9B and 9C, apull wire lumen 220 (see FIG. 9C) may terminate sufficiently proximallyfrom the retraction band 226 that a slot as shown may not be used.

The pull wire 222 may comprise a variety of suitable profiles known tothose skilled in the art, such as round, flat straight, or tapered. Thediameter of a straight round pull wire 222 may be between about 0.008″and about 0.018″ and in one embodiment is about 0.009″. In anotherembodiment, the pull wire 222 has a multiple tapered profile withsuccessively distal diameters of 0.015″, 0.012″, and 0.009″ and a distalflat profile of 0.006″×0.012″. The pull wire 222 may be made from any ofa variety of suitable materials known to those skilled in the art, suchas stainless steel or nitinol, and may be braided or single strand andmay be coated with a variety of suitable lubricious materials such asTeflon, Paralene, etc. The wire 222 has sufficient tensile strength toallow the sheath 114 to be retracted proximally relative to the core112. In some embodiments, the wire 222 may have sufficient columnstrength to allow the sheath 114 to be advanced distally relative to thecore 112 and stents 12, 14. For example, if the distal stent 12 has beenpartially deployed, and the clinician determines that the stent 12should be re-positioned, the sheath 114 may be advanced distallyrelative to the stent 12 thereby re-contracting and capturing that stenton the core.

In general, the tensile strength or compressibility of the pull wire 222may also be varied depending upon the desired mode of action of theouter sheath 114. For example, as an alternative to the embodimentdescribed above, the outer sheath 114 may be distally advanced byaxially distally advancing the pull wire 222, to release the stent 118(see FIG. 12). In a hybrid embodiment, the outer sheath 114 is splitinto a proximal portion and a distal portion. A pull wire is connectedto the proximal portion, to allow proximal retraction to release theproximal stent. A push wire is attached to the distal portion, to allowdistal advance, thereby releasing the distal stent. These constructiondetails of the catheter 100 and nature of the wire 222 may be varied tosuit the needs of each of these embodiments, as will be apparent tothose skilled in the art in view of the disclosure herein.

The stents 118 (see FIG. 12) are carried on the central support core112, and are contracted radially thereon. By virtue of this contraction,the stents 118 (see FIG. 12) have a cross section which is smaller thanthat of the conduits 32 and 34 (see FIG. 3), and they can be introducedinto these as will be described below. The stents 118 are preferablydisposed on a radially inwardly recessed distal portion 129 of thecentral core 112 having a smaller diameter than the adjacent portions ofthe core 112. See FIG. 12. This recess 129 is preferably defineddistally by a distal abutment such as a shoulder 124 which may be in theform of a proximally facing surface on a distal tip 122. See FIG. 12.Distal tip 122 has an outer diameter smaller than that of the stents 118when the stents are expanded, but greater than the diameter of thestents 118 when they are contracted. See FIG. 12. This abutment 124consequently prevents distal advancement of the stents 118 from the core112 when the stents 118 are contracted. See FIG. 12.

Proximal movement of the stents 118 (see FIG. 12) relative to the core112 is prevented when the stents are in the radially contractedconfiguration by a proximal abutment surface such as annular shoulder125. The distal abutment 124 (see FIG. 12) and proximal abutment 125 maybe in the form of annular end faces formed by the axial ends of annularrecess 129 (see FIG. 12) in the core 112, for receiving the compressedstents 118. See FIG. 12. In one embodiment, illustrated in FIG. 10A, theproximal abutment 125 is carried by a stent stop 218. Stent stop 218 maybe integral with or attached to the central core 112 (see FIG. 10), andhas an outside diameter such that it is in sliding contact with theinside surface of outer sheath 114 (see FIG. 10). The compressed stent14 will thus not fit between the stop 218 and the outer sheath 114 (seeFIG. 10).

The deployment device 100 typically has a soft tapered tip 122 securedto the distal end of inner core 112 (see FIG. 10), and usually has aguidewire exit port 126 as is known in the art. The tapered distal tip122 facilitates insertion and atraumatic navigation of the vasculaturefor positioning the stent system 118 (see FIG. 12) in the area of thebifurcation to be treated. The distal tip 122 can be made from any of avariety of polymeric materials well known in the medical device arts,such as polyethylene, nylon, PTFE, and PEBAX. In the embodiment shown inFIG. 10, the distal tip 122 comprises an annular recess 230 sized andadapted to allow a distal portion of the outer sheath 114 (see FIG. 10)to reside therein such that the transition between the tip and the outersheath comprises a smooth exterior surface.

The distal tip 122 tapers in one embodiment from an outside diameterwhich is substantially the same as the outer diameter of the outersheath 114 (see FIG. 10) at the proximal end 128 of the tip 122 to anoutside diameter at its distal end 130 of slightly larger than theoutside diameter of a guidewire. The overall length of the distal tip122 in one embodiment of the delivery catheter 100 is about 3 mm toabout 12 mm, and in one embodiment the distal tip is about 8 mm long.The length and rate of taper of the distal tip 122 can be varieddepending upon the desired trackability and flexibility characteristics.The tip 122 may taper in a linear, curved or any other manner known tobe suitable.

With reference to FIGS. 11B and 12, a distal portion of the central core112 preferably has a longitudinal axial lumen 132 permitting slideableengagement of the core 112 on a guidewire 170. The guidewire lumen 132preferably includes a proximal access port 172 and a distal access port126 through which the guidewire may extend. The proximal access port 172may be located at a point along the length of the catheter 100, as shownin FIGS. 11A and 11B, and discussed below (rapid exchange), or theproximal access port 172 may be located at the proximal end 102 of thecatheter 100 (over the wire) (see FIG. 9B). In a rapid exchangeembodiment, the proximal access port 172 is generally within about 25 cmof the distal access port 126, and preferably is between about 20 cm andabout 30 cm of the distal access port 126. The guidewire lumen 132 maybe non-concentric with the catheter centerline for a substantial portionof the length of the guidewire lumen 132.

FIGS. 11A and 11B illustrate a transition between a proximal shaft tube111 and a distal shaft tube 113 including a proximal guidewire accessport 172 and a guidewire lumen 132 (see FIG. 11B). The guidewire lumen132 (see FIG. 11B) may extend through a coextrusion, or may be aseparate section of tubing which may be bonded, bound by a shrink wraptubing, or otherwise held relative to the proximal shaft tube 111.

In the construction shown in cross-section in FIG. 11B, a proximal shafttube 111 having a pull wire lumen 220 is joined to a distal shaft tube113 having a continuation of pull wire lumen 220 as well as a guidewirelumen 132. In the illustrated embodiment, the proximal shaft tube 111extends distally into the proximal end of connector tubing 230. Amandrel is positioned within each lumen, and shrink tubing 236 is heatedto bond the joint. An opening is subsequently formed in the shrink wrapto produce proximal access port 172 which provides access to theguidewire lumen 132.

In one embodiment, the proximal shaft tube 111 comprises a stainlesssteel hypodermic needle tubing having an outside diameter of about0.025″ and a wall thickness of about 0.003″. The distal end 123 of thehypotube is cut or ground into a tapered configuration. The axial lengthof the tapered zone may be varied widely, depending upon the desiredflexibility characteristics of the catheter 100 (see FIG. 9B). Ingeneral, the axial length of the taper is within the range of from about1 cm to about 5 cm, and, in one embodiment, is about 2.5 cm. Taperingthe distal end of the hypotube at the transition with the distal portionof the catheter provides a smooth transition of the flexibilitycharacteristics along the length of the catheter, from a relatively lessflexible proximal section to a relatively more flexible distal sectionas will be understood by those of skill in the art.

Referring to FIG. 12, the distal end of a dual stent deployment catheteris illustrated, which is also provided with an optional balloon. Aguidewire 170 is illustrated as positioned within the guidewire lumen132. As can be appreciated by those of skill in the art, the diameter ofthe guidewire 170 is illustrated as slightly smaller (e.g., by about0.001-0.003 inches) than the inside diameter of the guidewire lumen 132.Avoiding a tight fit between the guidewire 170 and inside diameter ofguidewire lumen 132 enhances the slideability of the catheter over theguidewire 170. In ultra small diameter catheter designs, it may bedesirable to coat the outside surface of the guidewire 170 and/or theinside walls of the guidewire lumen 132 with a lubricous coating tominimize friction as the catheter 100 is axially moved with respect tothe guidewire 170. A variety of coatings may be utilized, such asParalene, Teflon, silicone, polyimide-polytetrafluoroethylene compositematerials or others known in the art and suitable depending upon thematerial of the guidewire 170 or central core 112.

As shown in FIG. 12, an inflation lumen 134 may also extend throughoutthe length of the catheter 100 to place a proximal inflation port influid communication with one or more inflatable balloons 116 carried bythe distal end of the catheter.

The inflatable balloon 116, if present, may be positioned beneath one orboth stents, such as stent 14 as illustrated in FIG. 12 or proximally ordistally of the stent, depending upon the desired clinical protocol. Inone embodiment, as illustrated in FIG. 12, the stent may be a selfexpandable stent which is initially released by proximal retraction bythe outer sheath 114 as has been discussed. The balloon 16 is thereafterpositioned in concentrically within the stent, such that it may beinflated without repositioning the catheter to enlarge and/or shape thestent. Post stent deployment dilatation may be desirable either toproperly size and or shape the stent, or to compress material trappedbehind the stent to increase the luminal diameter (e.g., angioplasty).In an alternate mode of practicing the invention, angioplasty isaccomplished prior to deployment of the stent either by a balloon on thestent deployment catheter 100 or by a separate angioplasty ballooncatheter (or rotational artherectomy, laser or other recanalizationdevice). The stent deployment catheter 100 is thereafter positionedwithin the dilated lesion, and the stent is thereafter deployed. Thus,balloon dilatation can be accomplished using either the deploymentcatheter 100 or separate procedural catheter, and may be accomplishedeither prior to, simultaneously with, or following deployment of one ormore stents at the treatment site.

As seen in FIGS. 9 and 9B, the catheter also includes a handpiece 140 atthe proximal end of the catheter 100. The handpiece 140 is adapted to beengaged by the clinician to navigate and deploy the stent system 118(see FIG. 12) as will be described below. The handpiece 140 preferablyincludes a control 150 adapted to control and indicate a degree ofdeployment of one or both stents. The control 150 is typically inmechanical communication with the sheath 114 such that proximalretraction of the control 150 results in proximal retraction of thesheath 114. Those skilled in the art will recognize that distal motion,rotational movement of a rotatable wheel, or other motion of variouscontrols 150 may alternatively be employed to axially move such asdistally advance or proximally retract the sheath 114 to expose thestent or stents.

The illustrated control 150 is preferably moveable from a first positionto a second position for partial deployment of the first stent 12, and athird position for complete deployment of the first stent 12. A fourthand a fifth positions may also be provided to accomplish partial andcomplete deployment of an optional second stent 14. The control 150 mayinclude indicia 160 adapted to indicate the amount of each stent 12 or14 which has been exposed as the sheath 114 is retracted relative to thecore 112. The indicia 160 may include dents, notches, or other markingsto visually indicate the deployment progress. The control 150 may alsoor alternatively provide audible and/or tactile feedback using any of avariety of notches or other temporary catches to cause the slider to“click” into positions corresponding to partial and full deployment ofthe stents 12, 14. Alignable points of electrical contact may also beused. Those skilled in the art will recognize that many methods andstructures are available for providing a control 150 as desired.

The catheter 100 may include a plurality of radiopaque markers 250 (seenbest in FIGS. 2, 10, and 10A) impressed on or otherwise bonded to it,containing a radiopaque compound as will be recognized by those skilledin the art. Suitable markers can be produced from a variety ofmaterials, including platinum, gold, barium compounds, andtungsten/rhenium alloy. Some of the markers 250A (see FIG. 2) may havean annular shape and may extend around the entire periphery of thesheath 114. The annular markers 250A (see FIG. 2) may be situated, inthe area of the distal end of the first stent 12, the distal end of thesecond stent 14, and in the area of the bridge 18 (FIG. 1) or spaceseparating the stents 12, 14. A fourth marker 252 may be situated atsubstantially the halfway point of the generatrix of the lower segmentof the second stent 14 situated in the continuation of the bridge 18 andof the diametrically opposite generatrix. FIG. 2 shows a marker 252 witha diamond shape and a small thickness provided along the outer sheath114 at a desirable position for determining the rotational position ofthe catheter within the bifurcation. The markers 250 and 252 (see FIG.2) may be impressed on the core 112, on the sheath 114, or directly onthe stents 12, 14 such as on the bridge 18, and not on the sheath 114.

With reference to FIGS. 10 and 10A, three markers 253 are shown disposedat a distal end of the second stent 14 and spaced at 120° relative toone another. Three markers 254 are also disposed at a proximal end ofthe first stent 12, and spaced at 120° relative to one another. Eachstent 12, 14 also includes a single marker 210 at its opposite end(e.g., the first stent 12 has a single marker 210 at its distal end, andthe second stent 14 has a single marker 210 at its proximal end). Ofcourse, other marker arrangements may be used as desired by the skilledartisan.

A central marker 252 makes it possible to visualize, with the aid of asuitable radiography apparatus, the position of a bridge 18 separatingthe two stents 12, 14. Thus allowing a specialist to visualize thelocation of the second stent 14 so that it can be correctly positionedin relation to the widened zone 46 and carina. The end markers 250A (seeFIG. 2) allow a specialist to ensure that the stents 12, 14 arecorrectly positioned, respectively, in the main/principal conduit 32(see FIG. 3) and the secondary/branch conduit 34 (see FIG. 3).

A diamond-shaped marker 252 as shown in FIG. 2 is, for its part, visiblein a plan view or an edge view, depending on whether it is orientedperpendicular or parallel to the radius of the radiography apparatus. Itthus makes it possible to identify the angular orientation of the stents12, 14 in relation to the bifurcation 30, so that the part of the secondstent 14 having the greatest expansion can be placed in an appropriatemanner in relation to the widened transition zone 46.

Methods of positioning and deploying a pair of dissimilar stents in anarea of a bifurcation will now be discussed with reference to FIGS. 3-6and 13-17. Although portions of the following discussion refer todelivery of two dissimilar stent portions, those skilled in the art willrecognize that a larger or smaller number of stents, and/or stentshaving similar expanded configurations may also be used while realizingcertain aspects of the present invention.

A method of delivering a stent system as described above generally andillustrated in FIGS. 13-17 includes locating the bifurcation 30 to betreated, providing a suitable delivery catheter 100, positioning thedistal portion 107 (see FIG. 9) of a delivery catheter with stents 12,14 (see FIG. 16) disposed thereon in the branch of the bifurcation to betreated, partially deploying the first stent 12 in a branch vessel 34,observing and adjusting the position of the first stent 12 if necessary,then fully deploying the first stent 12. See FIG. 14. The second stent14 is partially deployed (see FIG. 16), and preferably the position isagain observed such as by infusing contrast media through the pull wirelumen 220 (see FIG. 11B) under fluoroscopic visualization. The positionof the second stent 14 (see FIG. 16) may be adjusted if necessary, andfinally the second stent 14 is fully deployed (see FIG. 17). Methods ofnavigating catheters through blood vessels or other fluid conduitswithin the human body are well known to those skilled in the art, andwill therefore not be discussed herein.

The delivery catheter 100 may be constructed according to any of theembodiments described above such that the stents 12, 14 may beselectively deployed (see FIG. 17) by axially displacing the outersheath 114 along the delivery catheter, thereby selectively exposing thestent system 10. This may be accomplished by holding the sheath 114fixed relative to the bifurcation, and selectively distally advancingthe central core 112. Thus, the present invention contemplates deployingone or more stents by distally advancing the central core (inner sheath)rather than proximally retracting the outer sheath as a mode of stentdeployment. The stent system may alternatively be deployed by holdingthe central core fixed relative to the bifurcation and selectivelyproximally retracting the sheath 114. The catheter may also be adaptedto allow the sheath to be advanced distally, thereby re-contracting thepartially deployed stents on the central core 112 to allow repositioningor removal.

In order to visualize the position of a partially-deployed stent with asuitable radiographic apparatus, a contrast media may be introducedthrough the catheter to the region of the stent placement. Many suitablecontrast media are known to those skilled in the art. The contrast mediamay be introduced at any stage of the deployment of the stent system 10.For example, a contrast media may be introduced after partiallydeploying the first stent 12, after fully deploying the first stent 12(see FIG. 15), after partially deploying the second stent 14 (see FIG.16), or after fully deploying the second stent 14 (see FIG. 17).

The degree of deployment of the stent system 10 is preferably madeapparent by the indicators on the handpiece 140 (see FIG. 9) asdescribed above. The handpiece 140 (see FIG. 9) and outer sheath arepreferably adapted such that a motion of a control on the handpiece 140(see FIG. 9) results in proximal motion of the outer sheath 114 relativeto the distal tip 122 and the stents 12, 14 (see FIG. 17). The handpiece140 (see FIG. 9) and sheath 114 may also be adapted such that the sheathmay be advanced distally relative to the stents 12, 14 (see FIG. 17),thus possibly re-contracting one of the stents 12, 14 (see FIG. 17) onthe core 112. This may be accomplished by providing a pull wire 222having a distal end 223 (see FIG. 9E) attached to a portion of the outersheath 114, and a proximal end adapted to be attached to the handpiece140 (see FIG. 9). Alternatively, the handpiece 140 (see FIG. 9) may beomitted, and the retraction wire 222 may be directly operated by theclinician.

In an alternative embodiment, indicated by FIGS. 4-6, the first and/orsecond stent 12, 14 (see FIG. 6) may be deployed in a single motion,thus omitting the step of re-positioning the stent 12, 14 (see FIG. 6)before fully deploying it. The sheath 114 is then progressivelywithdrawn, as is shown in FIGS. 5 and 6, in order to permit the completeexpansion of the stents 12, 14.

In a preferred embodiment, the second stent 14 (see FIG. 6) is placed inclose proximity to the first stent 12 (see FIG. 6). For example, thedistal end 38 (see FIG. 6) of the second stent 14 (see FIG. 6) may beplaced within a distance of about 4 mm of the proximal end 42 (see FIG.6) of the first stent 12 (see FIG. 6), more preferably this distance isless than about 2 mm, and most preferably the first and second stents12, 14 (see FIG. 6) are placed within 1 mm of one another. Those skilledin the art will recognize that the relative positioning of the first andsecond stents 12, 14 (see FIG. 6) will at least partially depend on thepresence or absence of a bridge 18 (see FIG. 6) as discussed above. Theaxial flexibility of any bridge 18 (see FIG. 6) will also affect thedegree of mobility of one of the stents relative to the other. Thus, astent system 10 (see FIG. 5) will preferably be chosen to best suit theparticular bifurcation to be treated.

As mentioned above, the stents 12, 14 (see FIG. 6) may be self-expandingor balloon-expandable (e.g., made of a substantially non-elasticmaterial). Thus the steps of partially deploying the first and/or thesecond stent may include introducing an inflation fluid into a balloonon which a stent is disposed, or alternatively the stent may be allowedto self-expand. In the case of a balloon-expandable second stent 14 (seeFIG. 6), the balloon 116 (FIG. 12) on which the second stent 14 (seeFIG. 6) is disposed may be specifically adapted to correspond to theparticular shape of the second stent 14 (see FIG. 6). Specifically, sucha balloon will preferably have a larger diameter at a distal end than ata proximal end.

After complete expansion of the stents 12, 14 (see FIG. 6), the distalend of the delivery catheter 100 including the core 112 and theguidewire 170 may be withdrawn from the conduits and the vasculature ofthe patient. Alternatively, additional stents may also be provided on adelivery catheter, which may also be positioned and deployed in one orboth branches of the bifurcation. For example, after deploying thesecond stent 14 as shown in FIG. 6 or 17, the catheter 100 and guidewire170 may be retracted and re-positioned in the second branch vessel suchthat a third stent may be positioned and deployed therein.

Referring to FIG. 18, a second branch stent 13 may be deployed in thesecond branch, such that both branch vessels in the bifurcation arefully stented. The second branch stent 13 may be either a selfexpandable or balloon expandable stent such as those well known in theart and disclosed in part elsewhere herein. The second branch stent 13may be deployed before or after the main stent 14 and/or first branchstent 12. In one application of the invention, the main vessel stent 14and first branch stent 12 are positioned as has been described herein. Astent deployment catheter (not illustrated) such as a balloon catheteror self expanding stent deployment catheter is transluminally advancedto the bifurcation, and advanced through the main vessel stent 14. Thesecond branch vessel stent 13 may then be aligned in the second branchvessel, such that it abuts end to end, is spaced apart from, or overlapswith the distal end of the main branch stent 14. The second branchvessel stent 13 may then be deployed, and the deployment catheterremoved.

As will be clear to those skilled in the art, the stent system 10 andstent delivery system 100 described herein is useful in treating anumber of pathological conditions commonly found in vascular systems andother fluid conduit systems of human patients. Treatment with theapparatus can include re-establishing the appropriate diameter of abifurcation in cases of arteriosclerosis or internal cell proliferation,or in rectifying a localized or nonlocalized dissection in the wall ofthe conduit, or in re-creating a bifurcation of normal diameter whileeliminating the aneurysmal pouch in cases of aneurysm.

One or more of the stents deployed in accordance with the presentinvention may be coated with or otherwise carry a drug to be eluted overtime at the bifurcation site. Any of a variety of therapeutically usefulagents may be used, including but not limited to, for example, agentsfor inhibiting restenosis, inhibiting platelet aggregation, orencouraging endothelialization. Some of the suitable agents may includesmooth muscle cell proliferation inhibitors such as rapamycin,angiopeptin, and monoclonal antibodies capable of blocking smooth musclecell proliferation; anti-inflammatory agents such as dexamethasone,prednisolone, corticosterone, budesonide, estrogen, sulfasalazine,acetyl salicylic acid, and mesalamine, lipoxygenase inhibitors; calciumentry blockers such as verapamil, diltiazem and nifedipine;antineoplastic/antiproliferative/anti-mitotic agents such as paclitaxel,5-fluorouracil, methotrexate, doxorubicin, daunorubicin, cyclosporine,cisplatin, vinblastine, vincristine, colchicine, epothilones,endostatin, angiostatin, Squalamine, and thymidine kinase inhibitors;L-arginine; antimicrobials such astriclosan, cephalosporins,aminoglycosides, and nitorfurantoin; anesthetic agents such aslidocaine, bupivacaine, and ropivacaine; nitric oxide (NO) donors suchas lisidomine, molsidomine, NO-protein adducts, NO-polysaccharideadducts, polymeric or oligomeric NO adducts or chemical complexes;anti-coagulants such as D-Phe-Pro-Arg chloromethyl ketone, an RGDpeptide-containing compound, heparin, antithrombin compounds, plateletreceptor antagonists, anti-thrombin antibodies, anti-platelet receptorantibodies, enoxaparin, hirudin, Warafin sodium, Dicumarol, aspirin,prostaglandin inhibitors, platelet inhibitors and tick antiplateletfactors; interleukins, interferons, and free radical scavengers;vascular cell growth promoters such as growth factors, growth factorreceptor antagonists, transcriptional activators, and translationalpromotors; vascular cell growth inhibitors such as growth factorinhibitors (e.g., PDGF inhibitor—Trapidil), growth factor receptorantagonists, transcriptional repressors, translational repressors,replication inhibitors, inhibitory antibodies, antibodies directedagainst growth factors, bifunctional molecules consisting of a growthfactor and a cytotoxin, bifunctional molecules consisting of an antibodyand a cytotoxin; Tyrosine kinase inhibitors, chymase inhibitors, e.g.,Tranilast, ACE inhibitors, e.g., Enalapril, MMP inhibitors, (e.g.,Ilomastat, Metastat), GP IIb/IIIa inhibitors (e.g., Intergrilin,abciximab), seratonin antagnonist, and 5-HT uptake inhibitors;cholesterol-lowering agents; vasodilating agents; and agents whichinterfere with endogeneus vascoactive mechanisms. Polynucleotidesequences may also function as anti-restenosis agents, such as p15, p16,p18, p19, p21, p27, p53, p57, Rb, nFkB and E2F decoys, thymidine kinase(“TK”) and combinations thereof and other agents useful for interferingwith cell proliferation. The selection of an active agent can be madetaking into account the desired clinical result and the nature of aparticular patient's condition and contraindications. With or withoutthe inclusion of a drug, any of the stents disclosed herein can be madefrom a bioabsorbable material.

The bifurcation 30 shown in FIG. 3 has excrescences 35 which create anarrowing in cross section, which impedes the flow of the liquidcirculating in the conduits 32 and 34. In the case of a vascularbifurcation, these excrescences are due, for example, toarteriosclerosis or cellular growth. The stent system described hereinpermits treatment of this bifurcation by re-establishing the appropriatediameter of the conduits 32, 34 and of the widened transition zone 46.

As shown in FIG. 7, the stent system 10 can also be used to treat ananeurysm 242. An aneurysm 242 is defined as a localized, pathological,blood-filled dilatation of a blood vessel caused by a disease orweakening of the vessel's wall. Thus it is desirable to provide a“substitute” vessel wall in an area of an aneurysm. For this purpose,the first or second stent 12, 14 may be at least partially covered by afilm 240 which is substantially impermeable to the fluid circulating inthe conduits 32, 34. Many suitable films are known to those skilled inthe art such as polyester, polytetrafluoroethylene (PTFE), high andmedium density polyethylenes, etc. The film may be sewn onto the stents12, 14, or it may be folded around a stent such that as the stent isexpanded within the vessel 32, the film 240 is trapped and held betweenthe stent and the vessel wall. The stent then guides the liquid throughthe bifurcation 30 and consequently prevents stressing of the wallforming the aneurysm 242.

In some embodiments, each of the first (cylindrical) stent 12 and second(tapered) stent 14 can be provided on its own individual deliverycatheter. With reference to FIGS. 19-22, embodiments of stent deliverysystems for use in deploying a single stent for treatment of a pathologyat a bifurcation are described below.

FIGS. 19 and 20 illustrate a system configured to deploy a single stenthaving a substantially straight or cylindrical shape when in itsexpanded condition, for example, the stent 12 could be substantially thesame as the cylindrical stent 12 of the above embodiments. The systemgenerally includes an elongate delivery catheter 100 substantially asdescribed above and having a single stent 12 disposed on the distal endof the catheter. The stent 12 is surrounded by a retractable sheath 114having a plurality of radial restraints such as retaining bands 121. Inthe illustrated embodiment, five retaining bands 121 are provided toretain the stent 12 in a compressed condition. Alternatively, othernumbers of retention bands 121 may also be used. For example, one, two,three, four, or six or more retention bands 121 may be used as desiredfor a particular stent.

FIG. 20 shows the system of FIG. 19 with a proximal detail of the outersheath 114. The delivery system for use with the straight stent 12typically includes a stent stop 218 with an annular shoulder 125 whichthe proximal end of the stent 12 will abut as the sheath 114 isretracted. As shown in FIG. 20, the stent stop 218 will abut theproximal markers 254 (in an embodiment having such markers) as thesheath is retracted by a proximal force on the pull wire 222 which isattached to the sheath 114 at a retraction band 226.

FIGS. 21 and 22 illustrate a system configured to deploy a single stenthaving a substantially conical or otherwise tapered shape when in itsexpanded condition. For example, the conical stent 14 may be the same orsimilar to the main branch stent 14 described above. The system of FIG.21 generally includes an elongate delivery catheter 100 substantially asdescribed above and having a single conical stent 14 disposed on thedistal end of the catheter 100. The stent 14 is surrounded by aretractable sheath 114, which can include a radial retention structuresuch as a plurality of retaining bands 121. In the illustratedembodiment, four retaining bands 121 are provided to retain the stent 14in a compressed condition and resist imprinting into the sheath 114.This number of retaining bands is particularly suited to the conicalstent 14 according to the embodiment illustrated in FIG. 23A.Alternatively, other numbers of retention bands 121 may also be used.For example, one, two, three, five, or six or more retention bands 121may be used as desired for a particular conical stent.

FIG. 22 shows the system of FIG. 21 with a proximal detail of the outersheath 114. The delivery system for use with the conical stent 14 caninclude a stent stop 218 with an annular shoulder 125 disposed withinthe outer sheath configured to provide an edge against which the stent14 may abut as the sheath is retracted. The stent stop 218 of thepresent embodiment illustrated in FIGS. 21 and 22, comprises a slot 211in which the proximal marker 210 of the conical stent 14 may rest. Bycontrast, this slot 211 may be omitted in the embodiment illustrated inFIGS. 19 and 20 configured for use with a cylindrical stent, or ifunnecessary in view of the particular conical stent design.

A delivery system adapted for use with a single stent will often besized differently from the two-stent delivery system described above aswill be apparent to those of skill in the art in view of the disclosureherein. For example, the axial length of the stent receiving recess 129(see FIG. 12) in a single stent delivery catheter will often be somewhatshorter than a dual-stent catheter. In general, the axial length of thestent receiving recess 129 (see FIG. 12) in a single, tapered stentsystem for use in a bifurcation of the coronary artery will be withinthe range of from about 8 mm to about 18 mm, and often within the rangeof from about 10 mm to about 13 mm. The tapered stent for use incoronary applications is generally at least 10 mm in axial length, forexample, 10 mm, 11 mm, 12 mm, and 13 mm can be used. For coronaryapplications, the proximal unconstrained expanded diameter is typicallyin the range of from about 3 mm to about 6 mm, and often from about 3.5mm to about 5.5 mm, and in one embodiment the proximal expanded diameteris about 4.5 mm. The distal unconstrained expanded diameter is typicallyin the range of from about 5 mm to about 8 mm, and often from about 5.5mm to about 7.5 mm. In one embodiment of a tapered stent for use incoronary applications, the distal expanded diameter is about 6.5 mm. Inone embodiment, the outer sheath 114 and the inner stent receivingrecess of a single stent catheter can be about 11 mm shorter than thecorresponding parts in a two-stent system.

A tapered stent for use in carotid or biliary applications generally hasan axial length in the range of about 15 mm up to about 20 mm, and oftenbetween about 17 mm and about 19 mm. In one particular embodiment atapered stent for use in carotid or biliary applications has an axiallength of about 18 mm. For carotid or biliary applications, the proximalexpanded diameter is typically in the range of from about 8 mm to about12 mm, and often from about 9 mm to about 11 mm, and in one embodimentthe proximal expanded diameter is about 10 mm. The distal expandeddiameter is typically in the range of from about 11 mm to about 15 mm,and often from about 12 mm to about 14 mm. In one embodiment of atapered stent for use in coronary applications, the distal expandeddiameter is about 13 mm. In general, the distal expanded diameter isgenerally at least about 40% of the axial length, and often the distalexpanded diameter is more than 50% of the axial length.

FIGS. 23A and 23B illustrate a bifurcation stent 300 in accordance withanother embodiment of the present invention. The bifurcation stent 300has a first end 302 (see FIG. 23A) (which is sometimes referred to asthe proximal end 302) and a second end 304 (which is sometimes referredto as the distal end 304). The bifurcation stent 300 is generally formedfrom a series of segments 306 that are connected to one another by links312. Each segment 306 is formed from struts 308 that generally extend ina zigzag pattern, although the struts 308 can be provided in any of anumber of curved, sinusoidal or other shapes and patterns. In oneembodiment, the struts 308 extend substantially linearly from a proximalapex to a distal apex.

The proximal end 302 (see FIG. 23A) of the bifurcation stent 300includes a proximal marker support 328 for holding a proximal marker330. The proximal end 302 (see FIG. 23A) can include more than oneproximal marker support 328, such as two or three proximal markersupports 328, five proximal marker supports 328, seven proximal markersupports 328, or more. The proximal end 302 (see FIG. 23A) of thebifurcation stent 300 generally includes at least one proximal markersupport 328, and often includes an odd number of proximal markersupports 328.

The distal end 304 (see FIG. 23A) of the bifurcation stent 300 includesat least one distal marker support 324 for holding at least one distalmarker 326. More than one distal marker support 324 can be provided atthe distal end 304 (see FIG. 23A). For example, three distal markersupports 324 can be provided as is illustrated in FIG. 23A. In otherembodiments more than three distal marker supports 324 are provided atthe distal end 304 (see FIG. 23A) of the bifurcation stent 300, such asfive distal marker supports 324, seven distal marker supports 324, ormore.

In the illustrated embodiment, the marker support 324 is in the form ofan annular band 325 (see FIG. 23D) of material, defining an opening 327(see FIG. 23D) there through for receiving marker 326. The markersupport 324 may be formed separately from the stent and bonded thereto,using any of a variety of techniques known in the art such as brazing,soldering, welding and the like. Preferably, however, the marker support324 is integrally formed with the stent such as by cutting from tubestock using laser cutting or other etching procedure in the same processas the formation of the wall pattern of the stent. This avoids the needto have a bonded joint.

Referring to FIG. 23D, the annular band 325 defines an opening 327 forreceiving the marker 326. The annular band 325 and opening 327 may haveany of a variety of shapes, such as round, square, rectangular, oval, orother. In the illustrated embodiment, the opening 327 has an elongatedor oval configuration having a major axis extending in a circumferentialdirection and a minor access extending in an axial direction. Thecircumferential dimension of the opening 327 is greater than the axialdimension of the opening 327 in the illustrated embodiment, which allowsmaximization of the mass of the marker while minimizing the axial lengththereof. The circumferential dimension of the opening 327 may beanywhere within the range of from about 0.5 mm to about 1.0 mm and, inone embodiment, is about 0.7 mm. The axial dimension of the opening 327may be anywhere within the range of from about 0.3 mm to about 0.8 mm,and, in one embodiment, is about 0.5 mm. The width of the annular band325 taken in plan view as illustrated in FIG. 23D may be anywhere withinthe range of from about 0.08 mm to about 0.250 mm. In one embodiment,the width is about 0.12 mm. The width of the adjacent strut 329 takenfrom the same perspective may be anywhere within the range of from about0.075 mm to about 0.250 mm. In general, the width of the annular band325 is slightly greater than the width of the adjacent strut 329. In oneembodiment, the width of the adjacent strut 329 is about 0.1 mm.

Referring to FIG. 23E, there is illustrated a side elevational view of amarker 326 prior to attachment to a stent. The marker 326 generallycomprises a body portion 331 having a first cross sectional area and ahead 333 having a second, greater cross sectional area, to form agenerally mushroom shaped component. The body 331 has a leading end 335on the opposite end of the body from the head 333. The body 331 may havea generally cylindrical configuration, or may have a non-round crosssectional configuration such as oval, elliptical square or other. Thebody 331 is generally contemplated to have a diameter within the rangeof from about 0.3 mm to about 0.75 mm and, in one embodiment, about 0.5mm. The axial length of the component from the leading end 335 throughthe head 333 may be anywhere within the range of from about 0.25 mm toabout 0.5 mm and, in one embodiment, is about 0.38 mm. The diameter ofthe head 333 is preferably greater than the diameter of the body 331 byat least about 0.1 mm and, preferably, at least about 0.15 mm. In oneembodiment, the diameter of the head 333 is within the range of fromabout 0.5 mm to about 0.9 mm, and, in one embodiment, is about 0.7 mm.The axial length of the head 333 is preferably at least about 0.05 mmand no greater than about 0.2 mm. In one embodiment, the length is about0.08 mm. Dimensions outside of the recited ranges may also be used,depending upon stent dimensions and design.

In assembly, the marker 326 is positioned within the lumen of the stentand leading end 335 is advanced through the opening 327 of the annularband 325 from the inside (“lumenal side”) of the stent to the outside(ablumenal side) of the stent. This positions the integrally pre formedhead 333 against the inside surface of the stent. The body 331 isthereafter axially compressed such as by impact or other compressionagainst the surface 335, to reconfigure the surface 335 into acorresponding mushroom shape, thereby increasing its radial diameterrelative to the diameter of the body 331, and provides a locking surfaceon the outside surface of the stent. A marker starting with an axiallength of approximately 0.38 mm will be reduced in axial length tosomewhere within the range of from about 0.2 mm to about 0.3 mmfollowing compression. In one embodiment, the axial length of the markerpost compression is approximately 0.24 mm, when mounted in a stenthaving a wall thickness of about 0.160 mm. Compression may it beaccomplished by positioning the head 333 against an anvil surface withinthe stent, and impacting the surface 335 with a compression pin. Thesurface of the anvil and the compression pin may be planer or may beradiused, to curve the resulting end surfaces of the marker with aradius that corresponds to the radius of the stent.

A mounted marker is illustrated in FIG. 23F. In one implementation ofthe invention, the axial length through the marker is about 0.244 mm, ina stent having a wall thickness of about 0.160 mm. In oneimplementation, the marker 326 comprises gold, having a mass of about1.70 mg. Gold markers will generally have a mass in excess of at leastabout 1.0 mg, although the mass of the marker may be varied dependingupon the desired degree of visibility during the procedure.

The marker support 324 is positioned “off board” or beyond the end ofthe stent. In this context, the end of the stent is the plane whichextends transversally to the longitudinal axis of the stent, andcontains a plurality of apexes or peaks 320. This orientation positionsthe radiopaque marker 326 slightly beyond the end of the stent measuredin an axial direction. The length or diameter of the marker support 324measured parallel to the longitudinal axis of the stent is generally atleast 10%, in some embodiments at least about 20%, and may be at leastabout 30% or more of the axial length of the adjacent segment 306.

The proximal and distal markers 330, 326 can be any of a variety ofmarkers known to those of skill in the art, and can have any of avariety of shapes. The proximal and distal markers 330, 326 can includeany of the markers described herein. For example, the markers 330, 326can be radiopaque or have radiopaque properties. The markers 330, 326can be cylindrical (circular in a side view), diamond-shaped, square,frustoconical, or any other shape suitable for use with the bifurcationstent 300. The markers 330, 326 can be attached to the bifurcation stentin any of a variety of ways, including crimping, press-fitting, locking,screwing, or twisting them into the proximal and distal marker supports328, 324 with or without soldering, brazing, adhesives or otherattachment feature. In other embodiments the markers 328, 324 arepainted onto the segments 306, stents 308, and/or proximal and distalmarker supports 328 of the bifurcation stent 300.

The struts 308 of each cell segment of the bifurcation stent 300 formdistal peaks 320 and proximal peaks 322 as the struts 308 extend aroundthe perimeter of the bifurcation stent 300 in a zigzag pattern. Links312 connect adjacent segments 306 by extending in a distal directionfrom the distal peak 320 of one segment 306 to a proximal peak 322 of anadjacent segment 306.

The links 312 can have any of a variety of cross sectional shapes knownto those of skill in the art, such as rectangular, cylindrical, tapered,or any other shape. In one embodiment, the links 312 have a constanttransverse area through their length, and in other embodiments the links312 taper to a smaller cross-sectional area (e.g., diameter) along theirlength to increase flexibility of the bifurcation stent 300. Forexample, in one embodiment, the links 312 or at least some of the links,have an hourglass shape, such that they are wider at the link ends thanat the link middle portion. In other embodiments, the links 312 arewider at one end than at the other end. The link 312 can have across-sectional area substantially equal to, less than, or greater thanthe diameter of an adjacent strut 308. The links 312 may be selected ina variety of lengths. For example, in some embodiments, the links 312are no more than about 0.5 mm, no more than about 0.75 mm, or less thanabout 1 mm in length.

The bifurcation stent 300 can be enlarged from a collapsed, orreduced-diameter configuration to an expanded, or enlarged-diameterconfiguration, such as illustrated in FIG. 23A. When expanded, thebifurcation stent 300 has a proximal (upstream, as deployed) diameter316 that is smaller than its distal (downstream, as deployed) diameter318. A central lumen 334 extends through the bifurcation stent 300 fromits proximal end 302 to distal end 304. In some embodiments, the stent300 proximal diameter 316 is no more than about 3.25 mm, no more thanabout 4.75 mm, or no more than about 5.25 mm and the distal diameter 318is at least about 5.5 mm, at least about 7 mm, or at least about 8 mm.In some embodiments the stent 300 has a proximal diameter 316 in therange of about 2-4 mm and a distal diameter of about 4-7 mm. In otherembodiments, the proximal diameter 316 is in the range of about 3-5 mmand distal diameter 318 is in the range of about 5-9 mm. In otherembodiments, the proximal diameter is in the range of about 4-7 mm andthe distal diameter 318 is in the range of about 8-14 mm.

The length of each strut 308 from its distal peak 320 to its proximalpeak 322 defines a strut length 310. In addition, the distance betweendistal and proximal peaks 320, 322 of adjacent segments 306 defines alink length 314. Links 312 can be uniform in link length 314, ornon-uniform, as may be clinically desired. For example, varying linklength 314 can provide control over the flexibility of the bifurcationstent 300 between each segment 306. In addition, providing more links312 between adjacent cells 306 can improve repositionability of thebifurcation stent 300. For example, when a link 312 connects every pairof adjacent distal and proximal peaks 320, 322, the bifurcation stent300 will not bind up when deployed, and will exit the deploymentcatheter as an even cone (or flare).

FIG. 23B shows a rolled out flat view of the bifurcation stent 300 ofFIG. 23A to clearly illustrate one embodiment of a sidewall pattern of abifurcation stent 300. Strut length 310 and link length 314 are clearlyshown in FIG. 23B. In some embodiments, the struts 308 all have aboutthe same strut length 310. In other embodiments, the strut length 310 ofthe struts 308 of the distal most segment 306 are greater than the strutlength 310 of the struts 308 of the other segments. Strut lengths 310are often in the range of about 1-3 mm. The link lengths 314 aresometimes in the range of 0.5-0.75 mm, or less than about 1 mm.

The stent illustrated in FIGS. 23A and 23B has a tapered configurationin the unconstrained expanded configuration, and comprises four segments306. Depending upon the desired performance characteristics anddimensions of the stent, anywhere from one segment 306 to 10 or 12 ormore segments 306 may be utilized. In the embodiment illustrated in FIG.23C, for example, a stent having five segments 306 is illustrated in anexpanded configuration.

The bifurcation stent 300 illustrated in FIG. 23A has a tapered shape inits unconstrained, expanded configuration. However, any of a variety ofconfigurations may be used as a bifurcation stent 300, generally sharingthe characteristic that the distal and 304 has a greater cross sectionalarea than the proximal end 302 in an unconstrained expansion. Forexample, a flared bifurcation stent 300 is illustrated in FIGS. 24A-C.The flared bifurcation stent 300 of FIG. 24A includes, in oneembodiment, many of the same components as the bifurcation stent 300 ofFIG. 23A. However, the flared bifurcation stent 300 can have longerstrut length 310 (see FIG. 24A) segments 306 located at its distal end304 than at its proximal end 302.

The taper angle or flare configuration may be selected to accommodatethe particular bifurcation into which the bifurcation stent 300 is to bedeployed. For example, a bifurcation stent 300 can have a half-angletaper of at least about 20°, at least about 25°, or at least about 30°.In other embodiments the bifurcation stent 300 has a half-angle tapermore than 35°.

The bifurcation stent 300 often has a symmetrical taper angle or flareconfiguration such that the unconstrained, expanded taper angle or flareconfiguration is uniform about its outer surface. Such configurationsmay be advantageous when deploying the bifurcation stent 300 into asubstantially cylindrical bifurcation having a near circular crosssection. However, in other embodiments, where the cross section of thebifurcation is non-cylindrical (e.g., oval, elliptical, elongated,etc.), the bifurcation stent 300 can have a corresponding asymmetricaltaper angle or flare configuration. When asymmetrical, the taper angleor flare configuration as viewed from one side view of the bifurcationstent 300 is different than the taper angle or flare configuration asviewed from a different side view of the bifurcation stent 300. Ineither case, the stent can be configured to adopt the configuration ofthe native anatomy upon deployment.

Additional links 312 may be provided between adjacent segments 306 ofthe bifurcation stent 300. For example, in the bifurcation stent of FIG.23A, as best seen in FIG. 23B, the tapered bifurcation stent 300 hasseven links 312 connecting the most proximal segment 306 and the segment306 adjacent to it. The distal-most segment 306 is connected to thesegment 306 adjacent to it with four links 312. However, in the flaredbifurcation stent 300 of FIGS. 24A-C, the most proximal segment 306 isconnected to its adjacent segment with seven links 312, and thedistal-most segment 306 is connected to its adjacent segment 306 withseven links 312 as well.

In the illustrated embodiment, each segment 306 has approximately 14proximal apexes 322 and 14 distal apexes 320. Depending upon the desiredstent performance and intended anatomy, the number of apexes may bevaried considerably. Anywhere from approximately 6 apexes to 20 apexesor more may be used, depending upon desired performance. In theembodiment illustrated in FIG. 23A, the proximal segment 306 has 14distal apexes 320 and 7 links 312. The links 312 are spaced apart evenlyaround the circumference of the stent, such that every other apex isprovided with a link 312. Alternatively, links 312 may be provided onevery third apex, every fourth apex, or more. Typically, no fewer thantwo or three links 312 will be positioned between two adjacent segments306. In higher link density configurations, links 312 may be provided onevery two out of three adjacent apexes, three out of four, or four outof five or more, including providing a link 312 on every apex around thecircumference of a segment 306. As the ratio of links 312 to apexesincreases, certain functional characteristics of the stent may beimproved, however at the cost of reduced stent flexibility as will beunderstood by those skilled in the art.

When expanded, such as illustrated in FIGS. 23A and 24A, the bifurcationstent 300 has an expanded length 332 extending from its proximal end 302to its distal end 304. When compressed, the bifurcation stent 300 has acompressed length 336 extending from its proximal end 302 and distal end304 as well. In some embodiments, the expanded length 332 and compressedlength 336 are equal or substantially the same. In such cases, thebifurcation stent 300 is non-foreshortening or substantiallynon-foreshortening. In other embodiments, the expanded length 332 of thebifurcation stent 300 is less than the compressed length 336. Thedifference between the compressed length 336 and the expanded length 332can be no more than about 1%, no more than about 1.5%, no more thanabout 5%, or less than about 7%.

The bifurcation stent 300 is often self-expanding, although it can beballoon inflatable when desired. A self-expandable bifurcation stent 300can be made from pseudoelastic alloys, such as nickel titanium, orNITINOL®, or Elgiloy, any other pseudoelastic alloy known to those ofskill in the art. In addition, the bifurcation stent can be made fromstainless steel, polymers, or plastics.

In some embodiments, the bifurcation stent 300 is cut from tube, such asby laser cutting techniques known in the art. However, the bifurcationstent 300 can alternatively be formed by cutting the desired patterninto a sheet of material and wrapping the sheet into a cylindrical,frustoconical, or flared form. In other embodiments, the bifurcationstent is formed by weaving wire into the desired shape.

FIG. 25 illustrates a vascular bifurcation 400 into which a bifurcationstent in accordance with any embodiments disclosed herein may bedelivered. The vascular bifurcation 400 typically occurs at thebranching of a main vessel 402 into a first branch vessel 404 and asecond branch vessel 406. Fluid generally flows through the vasculaturefrom the main vessel 402 into each of the first and second branchvessels 404, 406. The direction of fluid flow 408 is generally in adownstream orientation from a proximal location 410 with respect to thebifurcation 400 to distal locations 412 with respect to the bifurcation400.

The carina 414 is formed at the point where the first branch vessel 404and second branch vessel 406 meet. The carina 414 generally has asaddle-like shape, and in many cases can provide smooth blood flow fromthe main vessel 402 into each of the branch vessels 404, 406.

A reference diameter 416 is sometimes determined as the inside diameterof the main vessel 402 at a location proximal of the first and secondbranch vessels 404, 406 and carina 414. For example, the referencediameter 416 can be the diameter of the main vessel 410 at a locationabout 2-4 mm, about 4-6 mm, about 5-7 mm, or about 5 mm proximal of thecarina 414.

In some cases, a lesion (not shown) is formed along the inside wall ofthe main vessel 402 proximal to the bifurcation 400. In such cases, thereference diameter 416 is generally the inside diameter of the mainvessel 402 at a location proximal to the lesion. For example, thereference diameter 416 can be the diameter of the main vessel 410 at alocation about 2-4 mm, about 4-6 mm, about 5-7 mm, or about 5 mmproximal of the lesion. In other embodiments, the reference diameter 416is the diameter of the main vessel 402 just proximal or upstream fromthe widening transitional zone. In situations where there is a lesion atthe bifurcation, the reference diameter 416 can be the diameter of themain vessel 402 just proximal or upstream from the lesion.

A carinal plane 418 extends in a direction transverse to the main vessel402 intersecting the main vessel 402 as it branches into both the firstand second branch vessels 404, 406 tangential to the carina 414. Theostium diameter 420 is generally the diameter of the main vessel 402 atthe carinal plane 418, across both branch vessels.

In some embodiments, it may be advantageous or clinically indicated todilate the stenosed aspect of bifurcation 400 before deploying thebifurcation stent 300. For example, a balloon catheter (not shown) canbe delivered to the bifurcation 400 and deployed such that wheninflated, the wall of the balloon contacts and applies outward force tothe vessel wall to either branch or the main vessel at the bifurcation400. This pre-dilation may be performed using any of a variety oftechniques, including using two guide wires and sequential and/orkissing inflations or balloons.

FIG. 26 illustrates the deployment of a bifurcation stent at abifurcation in accordance with one embodiment of the present invention.A second guidewire, which may be used to facilitate a predilation, hasbeen omitted for simplicity. A guidewire 430 is inserted into a branchvessel via a main vessel 402. The guidewire 430 acts as a rail overwhich a delivery catheter 432 may be advanced through a patient'svasculature. The distal end of the delivery catheter 432 can include anatraumatic tip 434 to minimize or to reduce damaging the inside wall ofthe vasculature as the delivery catheter 432 is advanced over theguidewire 430. A retractable sheath 436 covers a bifurcation stent 300that is mounted to the delivery catheter 432. When the bifurcation stent300 is self-expandable, retraction of the retractable sheath 436 allowsthe bifurcation stent 300 to expand from its compressed configuration(as shown in FIG. 26) to its expanded configuration (as shown in FIG.23A). The distal and proximal markers 326, 330 allow visualization ofthe bifurcation stent 300 and determination of its exact location withinthe vasculature.

To deliver the bifurcation stent 300 to the bifurcation 400 the deliverycatheter 432 is advanced along the guidewire 430 until the distalmarkers 326 of the bifurcation stent 300 are adjacent the carina 414, asillustrated in FIG. 27. Any of a variety of techniques well known tothose of skill in the art may be used to visualize the markers 326within the patient's vasculature.

Once the distal marker 326 of the bifurcation stent 300 is approximatelyaligned with the carinal plane 418 or just on the distal side of thecarinal plane 418, the retractable sheath 436 is partially retracted asillustrated in FIG. 28. The retractable sheath 436 is retracted enoughto expose the distal-most segment 306 of the bifurcation stent 300. Whenthe bifurcation stent 300 is self-expandable, the distal-most segment306 will partially self-expand as shown in FIG. 28. At the distal-mostsegment 306 expands, its distal markers 326 move apart from one another.The distal markers 326 are positioned approximately within the carinalplane 418 so that the distal peaks 320 of the bifurcation stent'sdistal-most segment 306 are at a location proximal of and adjacent thecarina 414.

The retractable sheath 436 is then further retracted in a proximaldirection to expose the second segment 306 adjacent the distal-mostsegment 306 of the bifurcation stent 300. The catheter 432 is also movedin a slight distal direction to advance the distal peaks 320 and distalmarkers 326 passed the carinal plane 418 so that at least the markersand optionally the distal peaks 320 are distal to the carinal plane 418,as illustrated in FIG. 29. At this point two adjacent struts 308 of thedistal-most segment 306 which form a distally open “v” or otherconcavity begin to straddle the carina 414. When straddling the carina414 a first strut 308 can reside at least partially within the firstbranch vessel 404, and a second strut 308 (which can be adjacent to thefirst strut 308) can reside at least partially within the second branchvessel 406. In other embodiments, when straddling the carina 414 a firststrut 308 is directed towards the first branch vessel 404 and a secondstrut 308 is directed towards the second branch vessel 406. The firststrut 308 can be adjacent the second strut 308. The exact position andorientation of the bifurcation stent 300 can be confirmed using any of avariety of visualization techniques as are known to those of skill inthe art.

The bifurcation stent 300 is advanced distally until the carina 414contacts the inside walls of the distally facing concavity leading toproximal peak 322, which is formed between adjacent first and secondstruts 308 (see FIG. 27) that are positioned within the first and secondbranch vessels 404, 406, respectively, as illustrated schematically inFIG. 30. The retractable sheath 436 may then be fully retracted tocompletely release the bifurcation stent 300 from the catheter 432. Whenreleased from the catheter 432, the bifurcation stent 300 will expand toits fully expanded configuration and will generally conform to theinside surface of the vascular bifurcation 400. When fully expanded, thedistal peaks 320 of the distal-most segment 306 of the bifurcation stent300 are positioned at least about 1 mm, and in some implementations fromabout 2 mm to about 4 mm distal of the carinal plane 418.

Once deployed, the bifurcation stent 300 can be post dilated to assureproper stent placement and orientation. For example, a balloon cathetercan be advanced to the bifurcation 400 and inflated at least partiallywithin the bifurcation stent 300. The balloon can be shaped such thatwhen inflated it provides additional expansion to the distal segment 306of the bifurcation stent 300. In addition, a balloon catheter can beused to expand a balloon expandable bifurcation stent 300 from itscompressed state to its expanded stated when delivered to thebifurcation, to achieve the deployed tapered configuration describedherein.

A branch stent 500 may optionally be delivered to either or both of thebranch vessels 404, 406, as illustrated in FIG. 31. The branch stent 500generally has a cylindrical shape when fully expanded in anunconstrained configuration. The branch stent 500 can include any of avariety of wall patterns or designs well known to those of skill in theart and may include cells having struts and peaks such as used with thebifurcation stent described in FIGS. 23A and 24A.

The branch stent 500 can be delivered over the guidewire 430 with thesame catheter 432 used to deliver the bifurcation stent 300.Alternatively, the catheter 432 used to deliver the bifurcation stent300 may be removed from the vasculature and a second catheter containingthe branch stent 500 may thereafter be provided. Any of the cathetersdescribed herein may be used to deliver the bifurcation stent 300 and/orthe branch stent 500.

In one embodiment, as illustrated in FIG. 31, a cylindrical branch stent500 is delivered to a branch vessel of the bifurcation 400 through thelumen 334 of the previously deployed bifurcation stent 300. The branchstent 500 is deployed such that the proximal end 504 of the branch stent500 partially overlaps the distal end 304 of the bifurcation stent 300.Proximal peaks 502 of the branch stent 500 can be positioned proximal ofthe carinal plane 418, thereby at least partially overlapping thedistal-most cell 306 of the bifurcation stent 300.

The stents, stent deployment systems, and methods described herein maybe adapted as mentioned above to treat any of a number of bifurcationswithin a human patient. For example, bifurcations of both the left andright coronary arteries, the bifurcation of the carotid, femoral, iliac,popliteal, renal or other coronary bifurcations. Alternatively thisapparatus may be used for nonvascular bifurcations, such as tracheal orbiliary bifurcations, for example between the common bile and cysticducts, or in the area of the bifurcation of the principal bile tract.

Although certain preferred embodiments and examples have been describedherein, it will be understood by those skilled in the art that thepresent inventive subject matter extends beyond the specificallydisclosed embodiments to other alternative embodiments and/or uses ofthe invention and obvious modifications and equivalents thereof. Thus,it is intended that the scope of the present inventive subject matterherein disclosed should not be limited by the particular disclosedembodiments described above, but should be determined only by a fairreading of the claims that follow.

1. A bifurcation stent, comprising: a plurality of segments extendingcoaxially end to end along a longitudinal axis of the bifurcation stentfrom a first end to a second end of the bifurcation stent, each segmenthaving a plurality of struts extending in a zig-zag pattern extendingaround the circumference of the bifurcation stent, wherein thebifurcation stent is expandable from reduced diameter to an expandeddiameter, the first end of the bifurcation stent having a largerdiameter than the second end when expanded; and an eyelet integrallyformed with the segment positioned adjacent the first end, andconfigured to receive a radiopaque marker therein.
 2. The bifurcationstent of claim 1, further comprising a radiopaque marker.
 3. Thebifurcation stent of claim 2, wherein the radiopaque marker ismushroom-shaped.
 4. The bifurcation stent of claim 2, wherein theradiopaque marker is press-fit into the eyelet.
 5. The bifurcation stentof claim 2, wherein the radiopaque marker comprises gold.
 6. Thebifurcation stent of claim 2, wherein the radiopaque marker comprisestantalum.
 7. The bifurcation stent of claim 2, wherein the radiopaquemarker is selected to have an electromotive force to match the stent. 8.The bifurcation stent of claim 1, further comprising a second eyeletintegrally formed with the cell positioned adjacent the second end andconfigured to receive a second radiopaque marker therein.
 9. Thebifurcation stent of claim 1, comprising at least two eyelets forreceiving a radiopaque marker, on the first end of the stent.
 10. Thebifurcation stent of claim 9, comprising at least three eyelets forreceiving radiopaque markers on the first end.
 11. The bifurcation stentof claim 9, further comprising at least two eyelets on the second end ofthe stent, for receiving radiopaque markers.
 12. The bifurcation stentof claim 1, comprising four segments extending coaxially end to endbetween a first end and a second end of the bifurcation stent, furthercomprising three eyelets integrally formed on a first end of the stentand one eyelet integrally formed on a second end of the stent.
 13. Astent, having a tubular body with a first end and a second end, thestent expandable from a first, reduced diameter to a second, enlargeddiameter, the stent further comprising at least a first radiopaquemarker positioned beyond the first end of the stent, and at least asecond and a third radiopaque markers positioned beyond the second endof the stent.